The present invention relates to a side vehicle-body structure of an automotive vehicle which comprises a center pillar, an upper end of which is fixedly joined to a roof side rail and a lower end portion of which is fixedly joined to a side sill, the center pillar having a closed cross section extending in a vertical direction which is formed by a pillar outer panel and a pillar inner panel or a pillar reinforcement.
In general, a structure shown in FIG. 14 is known as an example of a side vehicle-body structure of an automotive vehicle. As shown in FIG. 14, a vehicle-body lower portion of this structure comprises a side sill outer 71, a side sill inner 72, a side sill reinforcement 73, thereby forming a side sill 75 which is a vehicle-body reinforcing member having a side-sill closed cross section 74 extending in a vehicle longitudinal direction. Meanwhile, a vehicle-body upper portion of this structure comprises a roof side rail outer 76, a roof side rail inner 77, and a roof side rail reinforcement 78, thereby forming a roof side rail 80 which is another vehicle-body reinforcing member having a roof-side closed cross section 79 extending in the vehicle longitudinal direction.
Further, there is provided a center pillar 85 which is another vehicle-body reinforcing member, an upper end of which is fixedly joined to the roof side rail 80 and a lower end portion of which is fixedly joined to the side sill 75, wherein the center pillar 85 has a center-pillar closed cross section 84 extending in a vertical direction which is formed by a pillar outer panel 81, a pillar inner panel 82, and a pillar reinforcement 83.
According to the side vehicle-body structure of the automotive vehicle shown in FIG. 14, there are, as a structure to receive a side-collision load (a load generated in a collision of a barrier Z as a collision object) in a side collision, a structure shown in a broken line denoted by reference character α, in which the side sill 75 is displaced (moved) inward with no bending of the center pillar 85 and another structure shown in a two-dotted broken line denoted by reference character β, in which a lower portion of the center pillar 85 is bent.
In the former structure, no bending occurs substantially at a collision portion of the center pillar 85 in the side collision and the lower end portion of the center pillar 85 is displaced (moved) inward with a supporting point of its upper end portion, so that most of the side-collision energy is received at the side sill 75 and its vehicle-body lower structure. This structure adopts configuration in which the lower portion of the center pillar 85 extends relatively long in the vehicle longitudinal direction, and the center pillar 85 and the side sill 75 are welded without connecting a ridgeline formed at a vehicle-compartment inside of the center pillar 85 and the side sill 75. However, there is a problem in that the lower portion of the center pillar 85 extends in the longitudinal direction, so that a material yield may be low when pressing process is applied to the center pillar, thereby increasing costs improperly.
In the latter structure, the upper end portion of the center pillar 85 is welded to the roof side rail 80 and the lower end portion of the center pillar 85 is welded to the side sill 75, so that the center pillar 85 bends at the collision portion which the barrier Z collides with in the side collision (particularly, at the portion which a position Z1 of the barrier Z collides with). Herein, the side-collision energy is absorbed by the bending of the center pillar 85.
FIG. 15 is a side view of the side vehicle-body structure of the automotive vehicle which adopts the above-described latter structure. In FIG. 15, small rectangular portions indicated in white show a spot-welding portion.
In the conventional structure shown in FIG. 15, a joint flange portion 82a which is formed at a rear side of the pillar inner panel 82 is spot-welded to the pillar reinforcement 83 and the pillar outer panel 81 (see FIG. 11) at plural welding portions SW97, SW98, SW99. Further, an inner panel body 82c is formed between a front-side joint flange portion 82b of the pillar inner panel 82 and the rear-side flange portion 82a, and a ridgeline portion X9 is formed between the rear-side joint portion 82a and the inner panel body 82c such that the ridgeline portion X9 extends along a rear-end edge 82d of the joint flange portion 82a, that is, the ridgeline portion X9 extends in the vertical direction roughly in parallel to the rear-end edge 82d. 
The center pillar 85 of FIG. 15 is a structural object which receives the side-collision load and prevents deformation of a vehicle body on a vehicle-compartment side. Since the above-described ridgeline portion X9 has a high rigidity, the side-collision load is transmitted to the side sill 75 via the ridgeline portion X9. Herein, when a tearing-off stress transmitted from the ridgeline portion X9 increases, the welding portion SW99 of the pillar end peels off, so that the other welding portions SW98, SW97 peel off at once. Consequently, the proof stress, in a vehicle width direction, of the center pillar 85 decreases, and therefore there is a problem in that the degree of an inward displacement of the center pillar 85 may improperly increase.
In particular, in a vehicle, such as SUV (Sport Utility Vehicle), which has a high vehicle-height and the high side sill 75, since the center pillar 85 receives the side collision at its lower portion, the stress is concentrated at the lower portion of the center pillar. Accordingly, the welding portion SW99 of the lower end portion of the center pillar 85 is made to peel off by an excessive load or tore off together with a surrounding base metal. In FIGS. 14 and 15, reference numeral 86 denotes a floor panel and reference numeral 87 denotes a roof panel.
In the meantime, Japanese Patent Laid-Open Publication No. 2009-113769 discloses a structure, in which a center pillar composed by a pillar inner panel and a pillar outer panel is joined to a side sill composed by a side sill inner and a side sill outer, and plural ridgeline portions provided at the pillar outer panel are configured to extend toward welding portions of the pillar outer panel and the side sill outer, whereby the side-collision stress can be dispersed to the plural welding portions via the plural ridgeline portions.
However, configuring such that the ridgeline portions extend toward the welding portions at an area where the side-collision stress is concentrated may not be suitable in protecting the welding portions against the excessive load in order to prevent the peeling-off of the welding portions.
Further, US Patent Application Publication No. 2011/0210581 A1 discloses a structure, in which there is provided a center pillar, an upper end portion of which is fixedly joined to a roof side rail and a lower end portion of which is fixedly joined to a side sill, and plural D-shaped through holes for deformation control are formed at front-and-rear both faces of a lower portion of an outer reinforcement which is positioned inside the center pillar, whereby a base portion at a lower portion of the center pillar can be protected.
However, forming plural D-shaped through holes which are relatively large sized at an area where the side-collision stress is concentrated may improperly increase the degree of an inward displacement (movement) of the outer reinforcement of the center pillar in the vehicle's side collision. Also, since the through holes are formed at the outer reinforcement, it may be impossible to protect the welding portions of the pillar inner panel, so that there is problem in that deformation of the pillar inner panel becomes so large that the welding portions may peels off easily. Therefore, it has been desired to ensure the sufficient degree of load absorption at the center pillar and prevent an input of the excessive load to the welding portions of the pillar end portion.